1. Field of the Invention
The present invention relates to a method of fabricating a substrate, and more particularly, to a method of fabricating a substrate for a liquid crystal display. Although the present invention is discussed in detail with respect to a substrate for a liquid crystal display, the present invention is applicable to a wide variety of devices including substrates similar to those used in a display.
2. Discussion of the Related Art
Generally, in a liquid crystal display, upper and lower substrates are joined. A substrate having a pixel electrode and switching device in a matrix, and a substrate having a color filter arranged to realize colors and a common electrode are attached to each other. Liquid crystal is injected between the two substrates, which are in turn sealed. When an electric field is applied externally, the liquid crystal moves according to the electric field so that an image is displayed by light passing through the substrates.
As shown in FIG. 1, a conventional liquid crystal display includes liquid crystal 5 having light transmissivity that varies with electric field, a first transparent substrate 3 (lower substrate) on which electric wire is formed to apply an electric field to a selected portion, and a second transparent substrate 4 (color filter substrate). The liquid crystal 5 is injected between substrates 3 and 4. Then, they are sealed by a sealant 6. Polarizing plates 2-1 and 2-2 are attached to substrates 3 and 4. A back light 1 for producing light is fastened to the bottom of the lower substrate.
In the first transparent substrate, a scanning line, a data line, a pixel electrode, and switching means for controlling an electric field to the pixel electrode are arranged in a matrix. To the second transparent substrate, the common electrode and color filter are attached. Leads and pads for receiving external signals are formed on the substrates.
A method of fabricating such a liquid crystal display will be discussed below.
On a transparent substrate, such as glass, several hundred thousand to several million unit pixel electrodes are disposed along with control devices for controlling data to be applied to those pixel electrodes, and data lines and scanning lines for externally applying a video signal are formed. This constitutes first transparent substrate 3.
On another transparent substrate, a color filter and a common electrode for forming colors by passing light controlled only by the pixel electrodes are disposed to form second transparent substrate 4. After the lower and upper substrates are assembled, a sealant is spread thereon to seal them. The two substrates are arranged to be joined. The liquid crystal is injected therebetween, and finally the liquid crystal injection hole is closed so that the liquid crystal is not discharged externally.
After the liquid crystal sealing process, polarizing plates 2-1 and 2-2 are attached to the substrates. In order to externally apply a signal, a drive IC is connected to the leads. A back light, that is, light emitting means, and attaching means are assembled under the lower substrate to complete the liquid crystal display.
In fabricating the upper and lower substrates according to the conventional method, rinsing/deposition or etching equipment is used through several tens of processes. Here, physical forces may be applied to the transparent substrates during the processes. Further, the substrates undergo heating and cooling processes which can damage the substrates, if fragile.
In the conventional technique, transparent glass is used for the substrates in manufacturing the liquid crystal display. Commercially available glass assembly (upper and lower substrates combined) is usually 1.4 mm-thick, for example. To reduce the weight of the liquid crystal display, a single substrate of 0.7 mm, for example, has been used. In the conventional technique described above, if the thickness of the substrate is determined at the initial stage, the same thickness is maintained to the final product.
Since conventionally used glass is comparatively thick, it is protected against physical or thermal impacts during procedure. However, if a thin substrate is used from the initial stage, the yield will decrease due to damage or deformation. For manufacturing the lower substrate and liquid crystal filling processes, the process of heating or cooling between 200-300.degree. C. occurs more than ten times. In addition, a high-speed rotation process due to a rinsing or coating process is repeated. For this reason, the thickness of glass cannot become thinner. There are limitations in reducing the weight of a liquid crystal display. In order to solve these problems, the equipment must be improved or additional functions must be provided, which however would increase the cost of the final product.